Flood risk explained
What council flood layers mean when you are buying a home, in plain English. Coverage differs by city.
Flooding happens in different ways: rivers overflowing, rain running overland, water pooling in low spots, and planning rules for known hazard areas. Each council publishes its own flood datasets. Your iQHOME report checks the layers available for Auckland, Wellington, Christchurch, Hamilton, Tauranga, Rotorua, Dunedin, and Queenstown Lakes. See the full list on the homepage under What iQHOME checks for you.
Four flood-related layers
Flood plains: Areas modelled for river and stream flooding, typically based on a 1-in-100-year event. If your pin is in a flood plain, the property may be at risk of inundation from waterways during heavy rain.
Overland flow paths: Routes rainwater takes when it cannot drain fast enough, often downhill across roads, driveways, or sections. A property in or next to a flow path may see sheet flow or pooling during intense rainfall even if it is not beside a river.
Flood prone areas: Areas where water tends to collect on the ground during storms, including depressions, poorly drained pockets, or historic flooding locations identified by council.
Flood hazard areas: Planning-related flood hazard classifications used under Auckland Unitary Plan rules. These can affect building requirements, earthworks, or consent conditions even when flooding is less obvious day to day.
Regional Flood Exposure Model (2023)
Greater Wellington publishes indicative regional river flood exposure used in LIM-style fluvial flood views. It shows where modelled river flooding may reach during significant rainfall events across the Wellington region. This is regional desktop mapping, not a site-specific flood study for your building.
River and stormwater flood
Christchurch City Council combines floor-level viewer parcel assessments with modelled river flood extents for waterways such as the Avon, Heathcote, Styx, and Halswell. This helps show where river or stormwater flooding may affect a property during significant events.
River, overland, and regional flood
Waikato District and Hamilton City publish several flood layers: 100-year flood hazard and flood extents, overland flow paths, and Waikato Regional Council regional river flood mapping. Together these show river flooding, sheet flow across sections, and broader regional river exposure.
Rainfall flooding and plan areas
Tauranga City Council maps flooding from rainfall (floodplains, overland flowpaths, and depth bands) and flood hazard plan areas used in planning rules. This is separate from harbour inundation covered in the coastal guide.
Stormwater and river flood
Rotorua Lakes Council publishes stormwater flood (1% AEP) depth mapping and river flood modelling for the Utuhina catchment with future sea-level scenarios. Useful for low-lying urban sections and valley-floor properties.
District Plan flood hazard (2GP)
Dunedin City Council maps moderate and high flood hazard areas under the second-generation district plan. These show where council identifies fluvial or overland flood risk for planning and buyer due diligence.
ORC and local flood layers
Otago Regional Council and Queenstown Lakes District Council publish flood hazard area (2021 ORC), rainfall flooding, and damburst flooding layers. Relevant around lakes, rivers, and alpine catchments where dam-break or intense rainfall scenarios are modelled.
If flood layers appear at or near your pin, ask your lawyer about LIM notes, talk to your insurer, and consider whether a site-specific assessment is warranted. Confirm findings with the appropriate council. iQHOME is a starting point, not a final engineering answer.